As the era of cloud computing has begun, there is an ever increasing need for higher-speed information processing to process enormously increasing amount of information. In the era of personal computers, users spent long periods of time to deal with too large amounts of information. In the world of cloud computing, however, information is processed in real time, and therefore, users cannot spend time to process information.
Meanwhile, in order to process information at high speeds, SRAMs (Static Random Access Memories) and MPUs (Micro-Processing Units) are used. In the world of cloud computing, however, data is transmitted to and received from mobile terminals, and enormous amounts of information are used in real time. Therefore, SRAMs and MPUs that continually consume electrical power have the problem of power consumptions. To compensate for the large amount of power consumptions, large batteries are necessary. This is far from portable access to information on a daily basis.
To reduce the consumptions of electrical power, the expectations for development of nonvolatile memories are growing, and such development is being accelerated around the world. Examples of such nonvolatile memories include MRAMs (Magnetic Random Access Memories), FeRAMs (Ferroelectric RAMs), PRAMs (Phase-change RAMs), and ReRAMs (Resistance-variable RAMs). Of those memories, only MRAMs can cope with a very large number of rewriting operations, and have high write and read speeds. In view of this, MRAMs have the potential to realize nonvolatile working memories.
However, the write time and the read time of a MRAM are both approximately ten times longer than the write time and the read time of a SRAM. In a MRAM, the write time can be shortened by increasing the write current, and the read time can be shortened by increasing the read resistance difference. In this manner, higher speeds can be achieved. That is, in order to enable higher-speed reading, larger read resistance differences have been expected.
To realize high-speed operations equivalent to a SRAM with a MRAM, read outputs of the MRAM need to be increased, and the write current needs to be reduced. However, read outputs cannot be increased more than about 200% by any existing technique, and information consisting of the data “1” and the data “0” cannot be read at the same speed as that of a SRAM.